NSSDC Planetary Fact Sheet Time Series (1996–2025): A Longitudinal Archive of Solar-System Reference Parameters

NASA's NSSDC Planetary Fact Sheets (Williams, GSFC) have been the canonical "textbook parameters" reference for solar-system bodies — bond albedo, mass, surface pressure, scale height, satellite count, orbital elements, and dozens more — since the mid-1990s. The pages have been quietly revised many times over the past thirty years as new mission results landed, but no public dataset captured that revision history: a researcher citing "Mars bond albedo = 0.25" today has no easy way to know it was 0.16 from 1996 through 2010, or to reproduce a calculation against the value that was current when an older paper was written. This archive closes that gap. It bundles 913 distinct content versions of 13 NSSDC fact sheets — the Sun, all eight planets, the Moon, Pluto, plus the asteroid and comet summary sheets — pulled from the Internet Archive's Wayback Machine and parsed into a structured, time-indexed dataset spanning December 1996 to May 2025. Each capture is indexed by NSSDC's own "Last Updated" footer date (with the Wayback crawl timestamp as fallback) and yields up to 39 normalized field-value pairs per body, with original raw text and unit strings preserved for full provenance. The bundle ships the data in two equivalent forms — gzipped JSON for programmatic use and long-format CSV for tabular tools — alongside the complete raw HTML corpus and the stdlib-only Python scripts (fetch, parse, regenerate) that produced everything, so the entire pipeline is end-to-end reproducible from public sources. Designed as the historical-values backend for the planetarypy library, but usable independently for any work that touches reference-value drift, science-history studies, or reproducibility audits of older calculations. Update: Fixes in parsing increased the number of generated fields.